1. Technical Field
The following description relates to an image forming apparatus configured to form images on a printing sheet (hereinafter, simply referred to as a sheet), and in particular, to an image forming apparatus capable of duplex printing (i.e., capable of forming images on both sides of each sheet).
2. Prior Art
Conventionally, an image forming apparatus capable of executing duplex printing has been known. Such an image forming apparatus is typically provided with two sheet feeding paths: a main feeding path (i.e., a forward feeding path); and a re-feeding path (i.e., a reverse feeding path). The main feeding path is a path through which a sheet is fed from a sheet feed tray to a sheet discharge tray via a printing unit configured to form an image on a front surface of the sheet. The re-feeding path is a path through which the sheet, on which an image has been formed by the printing unit and fed on a downstream side of the printing unit, is fed to a position within the main path on an upstream side of the printing unit so that the sheet is fed along the main feeding path again. The sheet, which has been fed through the re-feeding path, is fed again along the main feeding path and reaches the printing unit such that a back surface thereof faces the printing unit. Thus, when the sheet is fed again along the main feeding path, an image is formed on the back surface of the printing sheet.
Generally, an image forming apparatus capable of executing the duplex printing typically requires a greater number of sensors than an image forming apparatus configured to form an image only on one surface of a sheet. For example, the image forming apparatus capable of executing the duplex printing, it is necessary to detect whether the sheet is fed to the re-feeding path, whether the sheet is jammed in the re-feeding path, and the like. As the number of the sensors increase, the image forming apparatus is upsized.
In consideration of the above problem, aspects of the present invention is advantageous that the number of sensors of an image forming apparatus capable of duplex printing is reduced so that the image forming apparatus can be downsized.
According to aspects of the invention, there is provided an image forming apparatus which has a sheet feed unit configured to feed a sheet toward a first feed path in a forward feed direction, a sheet tray configured to accommodate the sheet, the sheet tray being configured to be located at a feedable position at which the sheet feed unit is capable of feeding the sheet accommodated in the sheet tray and a non-feedable position which is different from the feedable position, a recording unit configured to record an image on the sheet which is fed from the sheet tray and guided by the first feed path, a roller provided on a downstream side, in the forward feed direction, with respect to the recording unit, the roller being configured to rotate in a first rotation direction to feed the sheet forwardly and a second rotation direction to feed the sheet reversely, a guide member including a first guide part defining a part of a lower surface of a second feed path which is connected to the first feed path at a first predetermined position which is located on a downstream side, in the forward feed direction, with respect to the recording unit and on an upstream side with respect to the roller, and at a second predetermined position which is located on an upstream side, in the forward feed direction, with respect to the recording unit, the guide member being configured to switch an orientation between a first orientation at which the first guide part define a part of the lower surface of the second feed path and a second orientation at which the first guide part is located at a lower position than a position at the first orientation, an interlocking mechanism which causes the guide member to have the first orientation in association with movement of the sheet tray to the feedable position, the interlocking mechanism causing the guide member to have the second orientation in association with movement of the sheet tray to the non-feedable position, a rockable member located at the first predetermined position, and a signal generating unit configured to output a signal corresponding to the position of the rockable member.
The rockable member is configured to rotate about an axis defined at a first end portion among a first position at which a second end portion at a downstream side in the forward feed direction with respect to the first end portion is supported by the guide member having the first orientation, a second position at which the second end portion is located at a higher position that the second end portion when located at the first position, and a third position at which the second end portion is located at a lower position that the second end portion when located at the first position.
According to the aspects of the present invention, by detecting a position of the rockable unit based on a signal generated by the signal generating unit, not only a position of the rockable unit but a status of a guide member, a position of a sheet tray and a current location of the sheet can be detected. In other words, the sensors used to detect the status of the guide member, the position of the sheet tray and the location of the sheet are commoditized. As a result, the size of the image forming apparatus can be reduced.